Allow shorter syntax for tasks with default configuration

Closes #194
Closes #240

Co-authored-by: Jaedle <dennis.jekubczyk@gmail.com>

internal/taskfile/task.go

@@ -1,5 +1,9 @@
 package taskfile
 
+import (
+	"errors"
+)
+
 // Tasks represents a group of tasks
 type Tasks map[string]*Task
 
@@ -20,5 +24,63 @@ type Task struct {
 	Silent        bool
 	Method        string
 	Prefix        string
-	IgnoreError   bool `yaml:"ignore_error"`
+	IgnoreError   bool
+}
+
+var (
+	// ErrCantUnmarshalTask is returned for invalid task YAML
+	ErrCantUnmarshalTask = errors.New("task: can't unmarshal task value")
+)
+
+func (t *Task) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var cmd Cmd
+	if err := unmarshal(&cmd); err == nil && cmd.Cmd != "" {
+		t.Cmds = append(t.Cmds, &cmd)
+		return nil
+	}
+
+	var cmds []*Cmd
+	if err := unmarshal(&cmds); err == nil && len(cmds) > 0 {
+		t.Cmds = cmds
+		return nil
+	}
+
+	var task struct {
+		Cmds          []*Cmd
+		Deps          []*Dep
+		Desc          string
+		Summary       string
+		Sources       []string
+		Generates     []string
+		Status        []string
+		Preconditions []*Precondition
+		Dir           string
+		Vars          Vars
+		Env           Vars
+		Silent        bool
+		Method        string
+		Prefix        string
+		IgnoreError   bool `yaml:"ignore_error"`
+	}
+	if err := unmarshal(&task); err == nil {
+		t.Cmds = task.Cmds
+		t.Deps = task.Deps
+		t.Desc = task.Desc
+		t.Summary = task.Summary
+		t.Sources = task.Sources
+		t.Generates = task.Generates
+		t.Status = task.Status
+		t.Preconditions = task.Preconditions
+		t.Dir = task.Dir
+		t.Vars = task.Vars
+		t.Env = task.Env
+		t.Silent = task.Silent
+		t.Method = task.Method
+		t.Prefix = task.Prefix
+		t.IgnoreError = task.IgnoreError
+
+		return nil
+	}
+
+	return ErrCantUnmarshalTask
 }